Theories about the evolution of consciousness relate in an intimate way to theories about the distribution of consciousness, which range from the view that only human beings are conscious to the view that all matter is in some sense conscious. Broadly speaking, such theories can be classified into discontinuity theories and continuity theories. Discontinuity theories propose that consciousness emerged only when material forms reached a given stage of evolution, but propose different criteria for the stage at which this occurred. Continuity theories argue that in some primal form, consciousness always accompanies matter and as matter evolved in form and complexity consciousness co-evolved, for example into the forms that we now recognise in human beings. Given our limited knowledge of the necessary and sufficient conditions for the presence of human consciousness in human brains, all options remain open. On balance however continuity theory appears to be more elegant than discontinuity theory.